The quick answer is that silk can be but the consumer must be aware and ask the right questions when shopping. Silk, like other protein fibers coming from living beings such as sheep and alpacas, can easily be created according to organic guidelines as they begin to be approved. And many silk fibers are probably already being produced in an organic environment, especially those produced in smaller villages and rural environments. To boost productions and improve efficiencies, large corporate farms will typically use heavy chemicals.
In the same way, the raising of domesticated silkworms and the life of wild silkworms is, by nature, sustainable. Silk fabric when produced by weavers on handlooms has a near zero energy footprint and satisfies most of the guidelines for sustainable fabric production. Silk produced in large powerloomed textiles factories must be evaluated on a company-by-company basis to determine their sustainability.
Ethical silk. Evaluating the ethics of silk is always a more complex and more personal question. Animal rights organizations are concerned about the destruction of several thousand domesticated silkworms to produce one pound of silk. Labor rights and Fair Trade organizations are concerned about the exploitive low wages often paid to silk textile workers.
Healthy Silk. While being a comparatively healthy and organic natural fiber, silk, like other fibers containing protein chains such as wools and even latex, is an allergen for some people. Silk allergies can cause asthma or allergic rhinitis with symptoms of runny nose and itchy eyes that are similar to hay fever. Medical researchers have found a wide variety of causes for a small number of people experiencing silk allergies: some are allergic to wild silk, some to domesticated silk, and some to micro-fine dust that can be given off by spun silk. Often, the allergies are traced to the diet of the silk worm – such as mulberry or oak leaves – which influence the protein chains found in the silk strands produced by the silk worm.
Some silk allergies come from excessive sericin in silk that has not been adequately degummed. Sericin is a complex protein produced by the silkworm that is sticky and coats the outside of the silk strand over the fibroin protein core. During the processing of the silk cocoon strands into silk threads, the silk workers use boiling hot soapy water that is slightly alkaline to degum the silk strands by dissolving much of the outer sericin layer. The waste silk, also called silk noil, from damaged cocoons and broken strands is often used as filling in silk duvets and lower quality spun silk fabrics. Sometimes the waste silk / silk noil is not sufficiently degummed resulting in excess sericin in the products that can result in silk allergic reactions for some people.
This process of degumming is also called scouring and is the first step in preparing silk for dyeing. Scouring and removing the sericin coating allows dyes to more easily penetrate the silk fibers. After scouring, silk is often bleached – sometimes with sulfur fumes to remove blemishes and leave the silk a uniform creamy color in preparation for dyeing.
Dyed Silk. As with any fabric, the dyeing of silk can also create health problems for people with chemical sensitivities and MCS. Because silk fibers are highly absorptive, Bombyx mori silk takes dyes exceptionally well and is one reason for the brilliance and luster of dyed silk fabrics. Domesticated silk fabrics are typically dyed with a mild acid dye or environmentally low impact fiber reactive dyes. Textile acid dye processes typically require high levels of chemicals, many of which have been classified by the Environmental Protection Agency (EPA) as being of moderate to high concern as carcinogens. Textile acid dyeing also typically discharges large amounts of contaminated waste waters that require treatment. Low impact fiber reactive dyes have a much smaller environmental footprint but still create some health problems for the chemically sensitive.
Wild silks and spun silks are harder to clean and bleach before dyeing and dyes do not take as well requiring heavier dyeing and more chemical processing before dyeing. If you wish to avoid dyes, your options are raw silk, natural undyed silk or golden hued Muga silk.
Weighted Silk. “Weighting” is a textile manufacturing practice peculiar to and particular to silk manufacturing and involves the application of metallic salts to add body, luster and physical weight to silk fabric. The reason for adding metals to silk fabric is to increase the weight of the fabric and, because silk fabric sells by the pound, the extra weight increases the selling price of the fabric. Generally, only the finer and more expensive reeled silks are weighted rather than the less costly spun silks. Some of the different salts of metals used to weight silk include chromium, barium, lead, tin, iron and sodium magnesium.
Weighting can increase the weight of a pound of raw silk by three, four, fivefold or more. Silk can be weighted because it is highly absorptive and the metal salts are easily absorbed into the silk fibers. Silk was originally weighted to make up for the loss of weight caused by degumming which removes the sericin reducing the weight of silk by about 20 percent. Silk is one of the strongest natural fibers but the metals used to weight silk cause it to lose much of its strength and durability if the weighting is not done properly. When shopping for silk, ask if the silk is weighted silk or pure-dyed silk. Pure-dyed silk is just colored with dye and not weighted. The metallic salts used to weight silk can cause health risks and problems for some people.
Finishing Silk. The purpose of the fabric finishing process is to give the fabric its final desired feel, appearance and care properties. A variety of environmental and health hazards can be introduced during the finishing phase of silk fabrics and garments. Water-soluble substances such as starch, glue, gelatin and even sugar are sometimes used to finish silk and provide extra body to the fabric.
Silk creases and wrinkles easily, especially when damp or wet. Some silk clothing manufacturers apply softeners, elastomers, and synthetic resins such as EPSIA – a silicone-containing epoxy crosslinking agent – to increase the dry and wet anti-wrinkling and crease-resistance performance of silk garments. With the family of silicone epoxy crosslinking agents (EPSIA, EPSIB and EPTA) this crease resistance occurs because chemical cross links occur between the silk fibroin strand and the epoxy groups. Research by Zaisheng Cai and Yiping Qiu in the Textile Research Journal (January 2003) reported “in conventional epoxide finishing of silk, organic solvents have to be used, which may be hazardous to the health of the exposed workers as well as the environment.”
Chemical treatments are also added to silk to improve anti-static, water and oil repellency, flame retardant, dimensional stability and other wash-and-wear properties that our easy-care culture seems to expect. Textile chemicals have become an integral and important component of conventional textile and clothing manufacturing. Textile chemicals, also know as textile auxiliaries, have two primary purposes: to increase the efficiency and lower the costs of conventional textile manufacturing; and to create special finishing effects and properties for the clothing.
The first category of textile auxiliaries and chemicals to improve manufacturing efficiencies are used in the spinning, weaving, scouring, bleaching and dyeing processes. Textile manufacturers claim that these textile chemicals can all be washed and removed from the final garments and are used to save time, reduce labor costs and reduce material costs. Environmental impact is seldom considered, especially in garment factories in developing countries, and many of the chemicals are discharged as untreated waste waters into rivers and ground water supplies.
The second category of textile chemicals are used mostly in the fabric and garment finishing processes and are intended to be permanent. These textile auxiliaries are supposed to give clothing special properties such as a smooth silky feel, easy care, mildew resiliency, flame retardant, and easy wear. Many of these chemicals are also toxic and suspected carcinogens.
So what’s the silk consumer to do? Caveat Emptor – Latin for “Let the buyer beware" - should be your guiding principal for evaluating all fabrics and clothing. Knowledge and information are your only resources when every emotional fiber screams out “I must have that Silk Chiffon Tie Neck Blouse ($198) from Brooks Brothers!” The warp and weft of silk fashion is emotion and compromise.
If your primary concern is healthy and organic silk then consider raw silk, noil silk, Muga silks or Eri silks that are undyed or dyed with low-impact, fiber-reactive dyes. The silk fabric should not be weighted or have any easy care or protective finishes. Silks produced in small villages by local weavers are usually the most pure.
If you are concerned about the ethics of silk raising then choose wild silk, spun silk or Eri silks which do not destroy the silk worm to harvest the silk cocoons. Also ask if the silk garments were produced according to Fair Trade principles which protect the workers involved in all phases of producing the clothing.
If you are concerned about sustainable and eco-friendly silk, then seek silks dyed using low-impact and fiber reactive dyes or vegetable dyes without any finishes. Handloomed silks are the most energy-neutral. Silk is also biodegradable and will decompose gracefully in landfills. Although, given its durability, silk is ideal for recycled ecofashion. NGO's and organizations such as the Institute for the Conservation of Tropical Environments are developing programs to assist poor rural communities in conservation efforts and economic development by developing their wild silk industries.
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